<template>
    <div class="pagination">
        <button @click="$emit('getPageNo', pageNo - 1)" :disabled="pageNo==1">上一页</button>
        <button v-if="startNumAbdEndNum.start > 1" @click="$emit('getPageNo', 1)"
            :class="{ active: pageNo == 1 }">1</button>
        <button v-if="startNumAbdEndNum.start > 2">···</button>

        <button v-for="(page, index) in startNumAbdEndNum.end" :key="index" v-if="page >= startNumAbdEndNum.start"
            @click="$emit('getPageNo', page)" :class="{ active: pageNo == page }">{{
                    page
            }}</button>

        <button v-if="startNumAbdEndNum.end < totalPage - 1">···</button>
        <button v-if="startNumAbdEndNum.end < totalPage" @click="$emit('getPageNo', totalPage)">{{ totalPage }}</button>
        <button @click="$emit('getPageNo', pageNo + 1)" :disabled="pageNo == totalPage">下一页</button>
        <button style="margin-left: 30px">共 {{ total }} 条</button>

    </div>
</template>

<script>
export default {
    name: "Pagination",
    props: ["pageNo", "pageSize", "total", "continues"],
    computed: {
        /* 计算出总共多少页 */
        totalPage() {
            /* 向上取整 */
            return Math.ceil(this.total / this.pageSize);
        },
        /* 计算连续页面的起始和结束页 */
        startNumAbdEndNum() {
            const { pageNo, continues, totalPage } = this
            let start = 0, end = 0;
            /* 不正常现象 总页数没有连续的页码多 */
            if (continues > totalPage) {
                start = 1
                end = totalPage
            } else {
                /* 正常现象 */
                start = pageNo - parseInt(continues / 2)
                end = pageNo + parseInt(continues / 2)
                if (start < 1) {
                    start = 1
                    end = continues
                }
                if (end > totalPage) {
                    end = totalPage
                    start = totalPage - continues - 1
                }
            }
            return { start, end }
        }
    }
}
</script>

<style lang="less" scoped>
.pagination {
    text-align: center;

    button {
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 55.5px;
        height: 48px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;

        &[disabled] {
            color: #c0c4cc;
            cursor: not-allowed;
        }
    }

    .active {
        cursor: not-allowed;
        background-color: aqua;
        color: #fff;
    }
}
</style>
